1. Field of the Invention
A number of methods have been developed for the rapid and accurate determination of analytes, such as haptens, antigens and receptors. One group of assays involves a bibulous support and an enzyme conjugate. The presence or absence of a dye on the support is indicative of the amount of analyte in the assay medium. In developing these assays, it is desirable to simplify the protocol. Protocols which involve numerous independent manual steps may result in the introduction of numerous errors. Also, there can be greater variation in the results between different technicians. Furthermore, a multi-step protocol is usually tedious unless the protocol can be automated. Automated assays normally require sophisticated machines, which would preclude the use of the assay outside of large clinical laboratories.
It is therefore of interest to be able to simplify presently existing assays by simplifying protocols and maintaining the ease of conducting the assay or enhancing the result. It is particularly important that the assay reagents be provided in predetermined amounts and measurements by the user are avoided.
2. Description of the Prior Art
U.S. Pat. No. 4,168,146 describes a test strip immunoassay. U.S. Pat. No. 4,299,916 describes an enzyme assay employing a bibulous support and enzyme binding to the support in relation to the amount of analyte in an assay medium. See also U.S. Pat. No. 4,391,904, a continuation-in-part of U.S. Pat. No. 4,299,916. U.S. Pat. No. 4,366,241 involves an alternative device for performing immunoassays. application Ser. No. 398,505, filed July 15, 1982 describes an enzyme chromatographic immunoassay involving two enzymes.
A single step heterogeneous assay is disclosed in U.S. patent application Ser. No. 602,297, filed Apr. 20, 1984. An internally referenced test strip immunoassay for morphine is described by Litman et al., Clin. Chem. (1983) 29: 1598-1603.